I have a well running battery-powered Heltec Wireless stick Lite (V3) with a DHT22 temperature sensor sending data every hour, and an (almost?) well running battery-powered Heltec Wireless stick Lite (V3) with a SEN0171 motion sensor sending data interrupt-triggered by the motion sensor but not more often then every 15 minutes. After placing the motion sensor setup 20 cm next to the temperature sensor setup, no motion data was sent for 3 hours (there was no motion) but afterwards the motion sensor got triggered every hour exactly when the temperature measuring board was sending, and this has been going on now for 16 hours. Unfortunately, the location of these devices is very remote and on-site trouble-shooting will be difficult. Any idea what is causing the motion sensor to get triggered by the board with the temperature sensor? Do I need a pull-down resistor for the motion detector? Could the 30 cm cable from the motion sensor to the connected board be the problem? Is there a minimum distance between the two Heltec Wireless Stick Lite (V3) ? Any ideas would be highly appreciated.
Almost certainly RFI being picked up by the motion sensor. Try moving 1m and then 2m apart and see if effect is same - will likely confirm. only solution then used screened cables and connectors for the sensor attachment, poss also look at putting in screened box with only its ant external (obviously needs to be able to radiate!). Not sure wher you are in the world but even say EU power levels in close proximity may be enough to trigger, in e.g. US with much higher TX pwr options situation even worse. If you are getting strong signal from both sensors despite
You might also consider dialing down Tx pwr or adding an attenuator in the temp sensor ant output?
Whilst I often have devices in close proximity for field or bench testing and checks (e.g. several trackers together on dashboard or rear window of vehicle when mapping etc.) I normally look to keep a min 1m seperation just in case, esp for sensitive or known poorly screened sensors, just in case…
Thanks a lot for your advise!! I am in the EU, but to my knowledge there are no sockets or power lines close to the sensors or boards. The issue is that I need full power in the antennas as the connection to the one gateway I can reach is already borderline. The next issue is that when placing both antennas 1 meter apart, one of them we likely get out of reach of the gateway (but I can try- very think stone walls with a small window). Currently, both boards are in their respective plastic boxes (about 8x8x4cm) with then antenna sitting on top of the box. The HT sensor sits in a hole on the side of one box, and the external motion sensor is connected via a 30 cm cable to the other box. For screening cables, which cable(s) exactly do I need to screen? What is the critical distance to the antenna of the hourly sending HT system, is it to the motion sensor itself, to the 30 cm cable it is connected with, or to the antenna or even board connected to the motion sensor? Which connectors exactly are you referring to? If I screen a box, won’t this disturb the signal of the antenna screwed into the top of the box?
What do you think about activating the pull-down resistor on the ESP32 for the motion sensor signal? Thanks again for any help!!!